Seems possible (though maybe not useful....). It would require total symmetry, so maybe you could scale the board down at the beginning of the game, then, as players move into areas, expand only those areas to full detail.

I don't quite agree. You can see this on the center map.The starter package contains a large and empty 25x24 map with the players next to each other in the middle.This one was quite hard to play well.Later, the preliminary rankings used a small version of this map, for which my bot played many draws agains players of varying strength simply by walking opposite directions and dividing territory evenly in two. On a slightly larger map my bot chooses to diverge from the symmetric behavior, simply because there is more room to switch from the left to the right side and back.

I see your point. I think in the beginning when the symmetry is obligatory you can simplify the map to maximize performance of calculations - nothing else. Just for the first 1-2 moves. Of course I can't prove it is a right assumption.

One way to test it would be to run a simulation on larger map (I assume that the best next move is known). Then simplify the board and check if the evaluation was the same. If it was the same i'm almost sure that it will take less CPU time.